Electron tube system



Aprf il??? M34 s. Y. WHsTE ELECTRON TUBE SYSTEM 4 Sheets-Sheet l Filed May 6, l930 Apri l?, 1934. s. Y. WHITE ELECTRON TUBE SYSTEM Filed May 6, 1930 4 Sheets-Sheet 2 CUEEE/VT JOU/205 CURRENT 600 CE prl W, H934., s. Y. WHITE M9557@ ELECTRON TUBE SYSTEM Filed May 6, 195o v 4 sheets-sheet 5 .S/NHL INPUT' ApriE 17, 1934. s. Y. WHITE ELECTRON TUBE SYSTEM I Filed May 6, 1930 4 Sheets-Sheet 4 YVIIIII Sla/VAL nvm/7' V V v Y V V V V V V V V @MM2/M Patented Apr. 17, 1934 UNITED STATES ELECTRON TUBE SYSTEM Sidney Y. White, New York, N. Y., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application May 6, 1930, Serial No. 450,070

1'1 claims.

My present invention relates to electron tube systems, and more particularly to cascaded electron tube systems.

In direct coupled cascaded tube systems, or in resistance coupled cascaded tube systems, it is frequently diicult to operate a pair of output tubes connected in so-called push-pull arrangement from a single input tube. Since these two types of systems have become of particular practical importance, I have developed an output system particularly suitable to them as well as to transformer coupled systems that hereinafter is termed a cascade output system.

An object of my invention is a cascade output system functioning within a transformer coupled, direct coupled, or resistance coupled electron tube system with the advantages of a pushpull output system insofar as signal currents are concerned, and without the diilculties inherent in the push-pull output system when employed in conjunction with a direct coupled tube system.

v-Other objects of my invention will become apparent as the description of my invention is developed with reference to the accompanying drawings in which Fig. l diagrammatically illustrates my cascade output system employed with a transformer in put system;

Fig. 2 diagrammatically illustrates my cascade output system employed with a direct coupled tube system, disclosed in my copending applications Serial Number 381,754, led July 29, 1929 and Serial Number 448,839 filed May l, 1930.

Fig. 3 diagrammatically illustrates a modification of the cascade output system of Fig. 1 when employed with the direct coupled tube system of Fig. 2.

Fig. 4 diagrammatically illustrates a modification of theV circuit arrangement of Fig. 3;

Fig. 5 diagrammatically illustrates a modification of the cascade output system disclosed in Figs. l and 2.

Fig. 6 diagrammatically illustrates a modification of the circuit arrangement of Fig. 5.

Fig. '7 diagrammatically illustrates a modification of the circuit arrangement of Fig. 4, and

Fig. 8 diagrammatically illustrates a modification of the circuit arrangement of Fig. 7.

In commercial radio receivers and amplifiers of the present, employing an electrodynamic speaker, the feature of the energization of the field coil of such a speaker without additional drain upon the filter system of the usual energizing source presents a serious problem. In the cascade output system to be hereinafter described I show the solution of this problem as an incidental feature thereof, but it is to be understood that the substitution of an impedance element in the place of the speaker eld coil may be made without departing from the spirit of my invention as defined in the claims appended hereto except wherein this feature is specifically included in certain of those claims. In all figures the coil designated `SFC may, therefore, be the I eld coil of the translating device or represent any other suitable impedance element.

Referring to Fig. 1, RT designates a full wave rectier tube energized from a source of alternating current AC through a power transformer ing connected to a loud speaker LS, preferably of the electrodynamic type, the terminals of the primary of the transformer OT being connected to the anodes of tubes VTz and VTz. The cathodes of tubes VTz and VT'z are connected in parallel and energized from a heating current transformer HT2 provided with a center-tap GT2 which is connected to the negative terminal G of the rectifier system through the eld coil SFC which is preferably that of the speaker LS and a resistance R, in this instance the resistance R bev,...\ ing so chosen that the potential difference between the points GT2 and G is equal to the normal grid bias of tubes VT2 and VT2.

The-grid of tube VT2 is connected to the terminal G through the secondary of an input transformer IT. The grid of tube VT'z is connected to the terminal G through a coupling resistance CR and to the plate of tube VTz through a coupling resistance CR and a coupling condenser CC.

The operation of this system is as follows: The space current of tubes V'I2 and VTz flowing through the speaker field coil SFC and the resistance R energizes the speaker eld and, due

to the potentials developed therein, the grids of c tubes VTz and VT2 are maintained at the proper average potential with respect to the cathodes thereof.

` Assuming a signal current energizing the transformer IT, the signal currents are amplified by the tube VTz with the resultant amplified signals passing through parallel paths, one of which is the section 1 of the primary of transformer OT and the other path through the condenser C'C and the coupling resistances CR and CR.

The signal currents at the grid of tube VTz connected to this latter path are in opposing phase with the signal currents in the input circuit of VTz and, if the coupling resistance CR is so chosen with respect to the coupling resistance CR" that there are impressed between the grid l'lO and cathode of tube VTz signal current potentials from the amplified output of tube VT2 equal to those developed between the cathode and grid of tube VT2, current variations in the sections 1 and 2 will be equal and additive in effect in the secondary of the transformer OT.

Such a cascade output system possesses all of the favorable characteristics of a push-pull output system with no need for by-passing the bias arm comprising the resistance R and the field coil SFC.

The system possesses the further feature that when the value of the resistance CR' approaches the normal input impedance of the tube VTz, the impedance of the connection CC, CR, CR' is of the order of 20 to 50 times that of the impedance of the section l of the output transformer OT, so that the substantially full output of tubes VTz and VT2 can be supplied to the output transformer OT, each tube being energized with signal current potentials of the order of that developed acrossthe secondary of transformer IT, Whereas in a push-pull system the potential in the secondaryof the pushpull input transformer is divided into two equal parts. For this reason and others, with a given signal input Ivoltage in ythe cascade output systemuescribed the overall amplifying ability is considerably greater than that Yof a push-pull connected system actuated by the same signal input voltage, I having actually Vconstructed systems having amplification factors' of from 'I to 32`Jtimes lthat of'a conventionally 4pushpull connected equivalent system.

Referring to Fig. 2, I'have indicated the rectifier and filter system of Fig. l merely by a symbol labeled "Current Source, and have modied the cascade'output system of Fig. l to adapt Athe same for use in a direct coupled cascaded electron tube system.

'T he terminal P of the source SF is connected vto the centertap of the primary of the'output transformer OT, the terminals of which transformerareconnected to the anodes of tubes VTz and VT'z. The cathodes of the tubes VTz and VTz are connected in the manner shown in Fig. 1,'b uti for simplicity I have omitted the showing of the heating current transformer HT2 and have provided the cathodes with centertaps GT2 and CTz connected to the negative terminal G of the source SF through the field coil'SFC, preferably that of the lou'd speaker or similar translating device, and resistance R, of higher value than vthat of resistance R in Fig. 1, the source having also a higher potential of output.

The grid of tube VTz is returned to the Itermi- Vnal vG through the anode-to-cathode path of a founelement tube VT1 and a 'stabilizing resistance S11/series related therewith.l The grid of tube VT1 is returned to the point A of'proper potential on the resistance R through the signal `input provided with a signal current condenser SC. The signal input maybe any source of variable voltage that it is desired to amplify." d A Thescreen grid of ltube VTi is connected Ato the point Bf on the resistance R of proper potential, and tube vVTi is provided with a hum-bucking condenser HBC connected between the cathode and a selected point D on the resistance R. The common connection between the plate of tube VTi and the grid of tube VTz is returned through a coupling resistance CR to a point vbetween two high resistances R and R connectedl between thewterminalP and the center tap GT2 vof the cathode of tube VTz, the additional load placed on the filter system being only that of the order of the small space current of tube VT1.

The functions of these various connections between tubes VT1 and VTz are described in detail in my copending applications herenbefore referred to and in papers published by myself and Edward H. Loftin in the February, March and April 1930 issues of Radio News, Experimenter Publications, Inc., Jamaica, N. Y.

In this arrangement of Fig. 2, the connection of the plate of tube VTz to the grid of tube VTz through the coupling condenser CC and the coupling resistances CR" and CR is returned to the point E on the resistance R of the proper potential to maintain the normal bias voltage on the grid of tube VT2 with respect to the cathode thereof.

The operation of this arrangement with respect to signal currents is as follows: Signal current voltages introduced at the signal input are amplified by the tubes VTi and VTz in the Anormal manner of. a direct coupled tube system, the output of tube V'Iz passing through parallel paths, one of which is the section l of the primary of output transformer OT and the other of which is through the condenser CC and the coupling resistances CR" and CR.

Analogous to Fig. l, the signal currents at the grids of the two tubes VTz land VT2 are in opposing phase, and if the coupling resistance CR is so chosen with respect to the coupling resistance CR" that there are impressed between the grid and cathode of tube VT2 signal current potentials equal to those developed between the grid and cathode of tube VTz, current variations in the sections l and 2 of the output transformer OT will be equal and additive in effect in the secondary of the transformer OT.

Such a cascade output system possesses all of the favorable advantages of the circuit of Fig. l

with the added feature of uniform with frequency amplification of the input signal currents inherent in direct coupled tube systems when compared with the non-uniform transfer of signal current energy through a transformer system indicated at IT in Fig. l.

This cascade output system likewise has an amplification factor several times that of a direct coupled push-pull system of the type disclosed by Paul P. Stoutenburgh in application Serial Number 443,294, filed April 11, 1930, with the use of a like number of tubes for the same reasons as set forth hereinbefor'e for the high amplification factor of the system disclosed in Fig. l when compared with the push-pull transformer coupled systems. v

In Fig. 3, I have shown a modification of the cascade output systems of Figs. l and 2 wherein I have embodied a feature of direct coupling between tubes VT2 and VTz by eliminating the coupling condenser CC of Fig. 2 and connecting the coupling resistance CR directly to the anode of tubel VTz and the coupling resistance CR to the terminal G of the source SF.

' An analysis of this circuit arrangement shows that the coupling resistances CR" and CR are series connected between the plate of tube VTa and the terminal G forming, a direct current potentiometer across the source, the bias of tube VT'2 being determined by the ratio of resistances CR" and CR.

With respect to the signal current potentials, this circuit arrangement is the same as previously described with reference to Figs. l and 2 with CII the additional feature that the condenser CC has een eliminated, which eliminates any frequency elective characteristic of the cascade output ystem.

In Fig. 4, I have shown a separate resistance Ri and a coil SFC for the tube VT2, the center taps CTz and CTz being connected together through a condenser SC2 of low impedance to signal currents. Otherwise the circuit arrangement is identical with that oi Fig. 3. The provision of separate resistances R and Ri for the tubes VT2 and VTz limits the reaction of the stabilizing system including resistance SR and connection of the grid of VTi to point A to potentials developed from the space current of tube V'I`2 only, so that ir" anything wrhin the system relating to tube VT'z should fail the tubes VTi and VTz carry on as a simple direct coupled tube system.

In Fig. 5, I have shown modincations of the cascaded output systems of Figs. l and 2 modied in that I have returned the coupling resistance CR to the center tap GT2 through a coupling condenser CC', and have maintained the grid or" tube VT2 at .ie same average potential as the grid of tube VTg, but isolated therefrom with respect to signal current iuctuations, by connecting between the two grids an isolating resistance IR.

In Fig. 6, I have shown a modification of the circuit arrangement of Fig. 5 in that I have connected the isolating resistance IR between the grid of tube VTz and the low potential terminal of the coupling resistance CR. In this manner I have been able to eirectively isolate the grid of tube VTz from the fluctuations at the grid of tube VTz since the combination of the condenser CC in conjunction with the resistance IR acts as a resistance-condenser nlter system.

In Fig. 7, I have shown a modification of the signal current coupling means of Fig. 6 between the tubes VTi and VTz. Herein, I have shown the coupling resistances CR and CR se conv nected between the plates of tubes VIz and VTz,

lli

or across the terminals of the output transformer OT. When so connected along the resistances CR and CR there are developed signal current potentials of similar phase to those along the sections l and 2 or" the primary of the output transformer O-. Therefore the resistances CR and CR should be so chosen that their junction point is at the same signal current potential with respect to the current owing in the output circuit of tube VT2 as the junction point between these same resistances is chosen with respect to the signal currents owing in the output circuit of the tube VTi of the preceding gures. These signal current potentials are transmitted to the grid of tube VTQ through a couplinfT condenser CC, thc grid bias of the tube VT2 being determined by the isolating resistance IR as in the previous gures.

In Fig. 8, l' have shown a modification of the system of Fig. 7 in that I have shown the grid of tube VT2 directly connected to the junction between the resistances CR and CR', and to the tap on the isolating resistance IR which is connected in shunt to the coil SFC, by which the bias on the grid of tube VT2 is determined, the resista-hoes CR, CR, IR, and R functioning as a potentiometer across the terminals P and G of the source.

While I have described my invention as embodied in several specific circuit arrangements, it

is to be understood that Various .modifications and combinations or" the features thereof may be made without departing from the spirit oi my invention as defined in the claims appended hereto.

Having thus described my invention, what I claim is:

l. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other termina-lof said source, a signal input system for one of said tubes, comprising a third electron tube the plate circuit of which is directly coupled to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means for maintaining the grids of each of said tubes at the proper bias potential with respect to the cathodes thereof.

2. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of elect-ron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a

signal input system for one of said tubes, com- A prising a third electron tube the plate circuit of which is directly couple to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance oi each of said tubes are substantially equal, and means for maintaining the grids or" each of said tubes at the proper bias potential with respect to the cathodes thereof.

3. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connecte-:l to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pairI to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means for stabilizing the average plate current of at least one of said pair of tubes.

4. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the icc lmeans for stabilizing the average plate current of each of said pair of tubes.

5. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said pri-mary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes, comprising a third electron tube the plate circuit of which is directly coupled to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means energized from the space current flow of said third electron tube for maintaining the grids of each of said tubes at the proper bias potential with respect to the cathodes thereof.

6. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means including a third electron tube for stabilizing the average plate current of at least one of said pair of tubes.

7. In a cascade output system, the combination of a source of power. an output transformer naving a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes comprising a third electron tube the plate circuit of which is directly coupled to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means for stabilizing the average plate current of at least one of said pair of tubes.

8. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source,

a signal input system for one of said tubes comprising a third electron tube the plate circuit of which is directly coupled to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are substantially equal, and means for stabilizing the average plate current of at least one of said pair of tubes.

9. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary. the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes comprising a third electron tube, the plate circuit of which is directly coupled to the grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varying impedance of each of said tubes are predetermined, and means for stabilizing the average plate current of each of said pair of tubes.

10. In a cascade output system, the combination of a source of power, an output transformer having a tapped primary, the tap of which is connected to one terminal of said source, a pair of electron tubes the anodes of which are connected to the terminals of said primary, potential developing elements connecting the cathodes of said tubes to the other terminal of said source, a signal input system for one of said tubes comprising a third electron tube, the plate circuit of which is directly coupled to Ythe grid circuit of said one tube, an auxiliary signal output circuit for said one tube, means coupling the grid of A the other tube of said pair to said auxiliary output circuit whereby the signal current variations in the primary of said output transformer due to the varyinsT impedance of each of said tubes are predetermined, and means within the plate-to-cathode circuit of said third electron tube for stabilizing the average plate current of each of said pair of tubes.

l1. In an electric system including two amplifying control-electrode discharge tubes having their output impedances arranged for push-pull operation, and means and connections for energizing electrodes of said tubes, the combination of a signal input system for impressing signals on one of said two tubes, an auxiliary impedance connected to the output of said one tube for diverting therefrom signal energy of the order of that impressed on the input thereof, means for impressing from said auxiliary impedance on the input of the other of said two tubes signal energy equal in magnitude but opposite in phase to that impressed on the input of said one tube, and means for maintaining the control electrodes of both said tubes at desired average potentials with respect to their associated cathodes.

SIDNEY Y. \VHITE. 

